Measurements in Helical Antennas

The circular polarization has some advantages over linear polarization. For example, if it is desirable to obtain a greater immunity to reflections of the radio signal caused by obstacles, one alternative is to use antennas that radiate in circular polarization. For the bands of VHF (Very High Frequency) and UHF (Ultra High Frequency), in this case the most commonly used antenna is the Helical Antenna. To evaluate the electrical characteristics of this type of antennas, we must use a different procedure from that employed for linear polarization antennas. This article will show that, without some additional care, the achievement of parameters such as radiation pattern and gain will present some distortion, thus not depicting the actual electrical behavior of the antenna. In this sense, here it is provided a guide to the effective realization of measures in circular polarization antennas with emphasis on the Helical Antenna.